1. Fields of the Invention
The present invention relates generally to apparatus and methods for mechanically performing single or multiple pass keratectomy for the correction of myopia, hyperopia and astigmatism, and, more particularly, to a surgical device that slices off a corneal disk by electromechanically driving only a reciprocating knife over the eye.
2. Discussion of Background and Prior Art
a. Eye Conditions
The treatable defective conditions of the optical system in the eye are well known. Myopia (nearsightedness) is a condition where the visual images come to focus in front of the retina of the eye resulting in defective vision of distant objects. Hyperopia (farsightedness) is a condition in which visual images come to focus behind the retina of the eye and vision is better for distant objects than for near objects. Astigmatism is a defect of an optical system (as a lens) in consequence of which rays from a point fail to meet in a focal point resulting in a blurred and imperfect image. In the human eye this defect of vision due to astigmatism of the refractive system of the eye is usually due to corneal irregularity.
b. Prior Solutions
(1). Corrective Glasses
For many years ophthalmologists and optometrists have routinely treated patients that had these visual defects by prescribing appropriate eye glasses and contact lens, and that practice is still widely practiced today. However, many people cannot afford glasses or contact lens, or find them to be a nuisance or a temporary solution.
(2). Surgical Solutions
Approximately thirty years ago ophthalmologists began to perform surgical procedures on the human cornea to correct these visual problems. The practice has come to be known as refractive surgery, and its purpose has been to surgically alter the cornea in order to change the refractive power of the cornea and thus eliminate the need for eye glasses or contact lens.
(a). Barraquer Movable Plate Microkeratome
One of the first procedures for refractive surgery was the Barraquer microkeratome which placed against the cornea a flat applanate surface supported with the knife (as in a plane) guided by spaced apart dovetailed guides which formed rails on a suction ring applied to the sclera and then manually passed across the cornea at an angle thereto a power driven reciprocating knife edge in a guideway to remove a round lamellar (sides parallel to the surface of the cornea) disk. The thickness of the cut disk was controlled by the thickness of a spacer plate (numerous plates for various thicknesses) and the cut disk rolled up into a groove between the spacer plate and the block carrying the knife as the cut was made. The cut disk was then frozen, lathed and replaced. The procedure was known as keratomileusis. This complex device required extremely high surgical skills and the device had limited applications.